A parasol in space to shield the Earth from the sun could prevent a
worldwide disaster due to the greenhouse effect, Michael Mautner, a New
Zealand physical chemist, has suggested to the World Future Society. The
warming of the planet due to human activities could cause the polar ice
caps to melt and oceans to rise, flooding heavily populated coastal
areas.

Current proposals to forestall the greenhouse effect, such as by
reforestation to absorb excess carbon dioxide, likely will prove
insufficient, Mautner believes, because of the staggering amount of
energy released by the sun. However, a space-based approach could
succeed. He proposes a climate-controlling fleet of screens that can be
placed in orbit between the Earth and the sun in order to redirect an
amount of energy up to 1,000,000 times larger than what is required to
deploy them.

To compensate for the predicted greenhouse effect, "we need to
screen out about three percent of the solar energy incident on Earth.
This requires a screen of about 2,000 square kilometers [1,200 square
miles]. This is a very large area. In fact, in terms of area at least,
the screen would be the largest object ever made by humans."
Mautner calculates that it is well within the capability of current
technology and suggests that the screen might be located about one-tenth
of the distance from the Earth to the sun.

He also foresees the use of space screens to protect people against
the rise in ultraviolet radiation believed to be occurring due to the
destruction of the ozone layer. The increase in UV radiation is expected
to result in a large increase in the number of individuals who suffer
from skin cancer due to exposure to the sun.

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